JPH01242172A - Coating method - Google Patents

Abstract

PURPOSE:To surely prevent sagging by rotating a material to be coated on its horizontal axis until a paint is set in a drying stage and sagging of the paint is not caused. CONSTITUTION:Dust is removed in a stage P1 while intermittently rotating a body W. A paint is sprayed in a stage P2 by using a paint which sags at least in one of the stages P3 and P4 and does not sag on the coated surface for at least one minute. The body W is then sent to the stage P3. The body W is rotated on the rotation axis (l) extending in the horizontal direction in the stage P3. Setting is carried out in the stage P3 in the atmosphere at 40-60 deg.C, and baking is carried out in the stage P4 in the atmosphere at 140 deg.C. Since the body W is rotated in the stages P3 and P4, the paint is dried without causing sagging. By this method, a high-quality coated surface having high smoothness is obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a coating method.

(Prior art and its problems) When painting the outer surface of an object to be painted, such as an automobile body, there are a preparation process for removing dust adhering to the object, a process for applying paint to the object, and a coating process. and a drying step of drying the painted paint. This drying process is generally carried out in two stages: a cerading process and a sintering process. It is carried out in a temperature atmosphere of 40° to 60°C (after baking, the baking temperature is usually 140°C).

7. The object to be coated is usually transported by means of a conveyor such as a trolley and undergoes the above-mentioned preparation process and drying step, but the posture of the object to be coated is It is performed while maintaining a predetermined posture.

By the way, smoothness (flatness) is used as a basis for evaluating the quality of the painted surface (17), and the higher the smoothness, the smaller the degree of unevenness of the painted surface, and the better the painted surface. It is already known that in order to improve the smoothness of the painted surface, it is sufficient to increase the thickness of the paint film, that is, the film thickness of the applied paint.

- On the other hand, paint "
This sagging occurs when the applied paint flows downward when subjected to 1 gravity, and the thicker the paint coated at one time, the more likely it is that sagging occurs. The cause of this phenomenon is ultimately the effect of gravity, and therefore it tends to occur on a surface of the object to be coated that extends in one direction, that is, a so-called vertical surface.

Therefore, on surfaces extending in the horizontal direction of the object to be coated, that is, so-called lateral surfaces, where the amount of "sagging" of the paint is less of a problem, it is possible to apply the paint to a greater thickness than on the vertical surfaces. In addition, even if the 1'y of the paint film on the drawing surface and the 1 thickness of the paint film on the vertical surface are the same, the unevenness will be reduced on the horizontal surface due to a slight flow of the paint that does not cause sagging, and the unevenness will be reduced on the horizontal surface. This results in better smoothness than on the surface.

From the above-mentioned point of view, conventionally, in order to prevent the paint from "sagging" and obtain a painted surface with as much smoothness as possible, painting was done using a paint with as little fluidity (low viscosity) as possible. was. The ``sag limit'' at which paint sag occurs on the vertical surface was a maximum coating film thickness of about 40 μm for conventionally widely used thermosetting paints. More specifically, paint sag tends to occur at the beginning of the setting process and at the beginning of the baking process, especially at the beginning of the baking process. The thickness is determined, and the maximum value of the determined thickness, ie, the sagging limit value, is approximately 40 μm. Therefore, in order to obtain a coating with even greater absolute smoothness, conventional coating methods require repeating the series of processes from coating to baking multiple times, such as by applying two coats. It was necessary to do it.

The present invention has been made in consideration of the following two circumstances, and it is an object of the present invention to provide a coating method that allows a coated surface with greater smoothness to be obtained with the same coating thickness. The purpose is -4.

(Means and effects for solving the problem) The present invention basically improves the fluidity of the paint by appropriately changing the direction of gravity acting on the paint applied to the object to be coated. By actively taking advantage of this, you can obtain a coated surface with greater smoothness for the same coating thickness. Specifically, the configuration is as follows. That is, in a painting method that includes a painting process of applying paint to an object to be painted and a drying process of drying the paint applied to the object, in the drying process, there is a large flow that causes the paint to sag. The object to be coated is rotated around a substantially horizontal axis until the paint is hardened to a point where the paint no longer drips. The configuration is as follows. .

In this way, in the present invention, the direction of gravity acting on the paint applied to the object to be coated is changed by rotating the object in the direction of the water, so that the paint does not sag. It will be dried without any drying.

According to the present invention, the film thickness of the paint applied per coat can be made much thicker than conventionally, and it is possible to obtain an extremely good coating whose smoothness far exceeds the level conventionally considered to be the limit. can.

Furthermore, even when the thickness of the film is the same as in the past, the fluidity of the paint can be utilized to create an excellent coated surface with fewer irregularities, that is, greater smoothness.

Furthermore, if you try to obtain a painted surface with the same smoothness, for example, the same level of smoothness as that obtained with conventional painting methods,
The film thickness of the coating material to be applied can be made thinner than that of the conventional method, and the coating thickness of the coating material used can be reduced by the amount that can be obtained.

Of course, paints that cause "sagging" even when applied thinly,
It can be obtained by reducing the components that impair fluidity by a certain percentage from conventional paints (conventional paints contain hybrid agents to reduce fluidity in order to improve the sag limit). ).

Furthermore, since the rotational speed of the object to be coated is set according to the maximum dripping speed of the paint, it is possible to reliably prevent paint from dripping due to insufficient rotational speed.

(Example) Hereinafter, an example of the present invention will be described based on the attached drawings.

Figure 1 shows the overall process for painting an automobile body W as an object to be coated, and each process is indicated by Pi-Pi.

First, the body W, which has been completely coated by electrocoating in a known manner, is sent to the preparation step PI while being held on a trolley. In this preparatory step PI, dust inside and outside the body W is removed by, for example, air blowing or vacuum suction. After that, in step P2, paint is sprayed onto the body W. Then, the paint is dried in a setting step P3 and a baking step P4.

If steps 1) 1 to P4 are for intermediate coating, the body W is sent to the final coating stage after step 1) 4. Also,
If steps 1) l to 1) 4 are overcoat rivers, body W
is transported to an assembly line in a known manner.

Dust removal in the construction process P1 is performed while rotating the body W around the horizontal axis, as shown in FIG. That is, for example, first, the rotation of the body W is stopped in the state shown in FIG. 2(a) to remove dust, and then the dust is removed as shown in FIG. 2(b).
The posture of the body W is changed to the state shown in FIG. In this way, as shown in (c), (d)...(i) in FIG.
Dust is removed while rotating intermittently.

In this way, by removing dust while rotating the body W, it is possible to remove dust adhering to closed sections such as the inside corners of the roof panel and side sills of the body W, i.e., if the body W is not rotated. It becomes possible to completely remove even the garbage that does not fall.

First, in the example, spraying of paint in P2 caused sag in at least one of the drying steps P3 or Pi, and the coated surface after painting was completed did not sag for at least 1 minute. (Examples of such paints will be described later). This value of 1 minute corresponds to the fact that it takes less than 1 minute from the start of painting to the completion of painting the entire body W. More specifically, until the entire painting is completed on one body W, sag is prevented from occurring in the part where the painting is most completely completed to ensure that sag does not occur in the painting process P2. It is said to be designed to prevent

The thickness of the coating film can be made thicker than the conventional limit since sagging may occur during the drying process 1) 3 or 4). Of course, it is optional to use the same thickness as the conventional one or a thinner thickness.

After P2, the process moves to P3, a setting process. In this setting step P3, the body W is rotated horizontally as shown in FIGS. 2(a) to 2(i). That is, the body W is rotated around a rotation axis β extending in the horizontal direction, and in the embodiment, this rotation axis β is
It is assumed that it extends in the front-back direction. Note that the temperature atmosphere in this setting step P3 is set to room temperature in the example, but it may be set to an appropriate temperature in a lower temperature range than the temperature atmosphere in the next baking step P4, such as 40° to 60°C. It is possible. Of course, this setting process P3 is to volatilize the low boiling point content in the paint in advance, and this will prevent the formation of pinholes on the painted surface due to the rapid volatilization of the low boiling point content in the next baking process P4. has a defense of 1L.

In the baking step P4, the paint is baked in an atmosphere at a temperature of, for example, +40°C. Even with this Pi, P
2 (a) to (i)
The body W is rotated in the horizontal direction as shown in FIG.

As mentioned above, P3. The rotation of the body W in the horizontal direction at P4 dries the paint without causing any sagging. As a result, a high-quality coated surface with extremely high smoothness, which could not be obtained with the conventional coating force d, can be obtained.

The relationship between paint Y, sag limit, 1r, mito, and 11 roll Figure 3 shows the influence of coating film thickness on the sag limit. FIG. 3 shows three cases in which the thickness of the coating film is +11i: 40 μm, 53 μm, and 65 μm. It is understood that for any of these thicknesses, peaks of "sag" occur both at the beginning of the Cerati-Nino process and at the beginning of the first baking process. In addition, the sag limit is the value when sagging of 1 to 2 mm occurs per minute (the painted surface is considered to be defective if the sag of 2 mm/min or more is visually observed). The maximum coating thickness that can be obtained within the range below the limit is about 40 μm with conventional paints.

On the other hand, Figure 4 shows the effects on smoothness when the body, f W, is rotated in the horizontal direction and when it is not. (conventional painting method). FIG. 4B shows a case where the body W is rotated 9Q' and then reversed (forward and reverse rotation between FIG. 2(a) and (C)). FIG. 4C shows a case where the body W is rotated by 135 degrees and then reversed (forward and reverse rotation between FIG. 2 (1) and (d)). Figure 4 (1) shows the case where the body (W) is rotated by 18 degrees and then reversed (Figures 2 (a) and (e)).
forward and reverse rotation). Fig. 4E shows the case where the body W is continuously rotated in the same direction (Fig. 2(a)
), (b), (c)... Take the posture in the order of (i),
(Go back to (a) again).

As is clear from Fig. 4, for the same coating film, it is better to rotate the body W (Fig. 4 II, C, D).
, E), thicker smoothness can be obtained than in the case without rotation (see Fig. 4). Also, even with the same rotation, 36o°
It is understood that it is preferable to rotate in the same direction in order to improve smoothness. Of course, if the body W does not rotate, there is a limit to the thickness of the coating film, so there is a limit to how much smoothness can be increased.

By the way, assuming the thickness of the coating film is 65μm, the body W is 36mm.
When rotated by 0°, the obtained smoothness is 1. r87J in G (lower limit of 1.0 in PGD value)
It is. Moreover, when the thickness of the coating film is 40 μm,
If the body W does not rotate, 1. r58J in G (P
The lower limit of GD value is 0.7), whereas when the body W is rotated 360 degrees, it is 1. r68J in G (PG
F limit value of 0.8 in D value).

As is known, IG (image cross) in mapping sharpness indicates the ratio of sharpness to mirror surface (black glass) as 100, and PGr) indicates the degree of discrimination of reflected images. This is a value at which the smoothness of the painted surface decreases as it decreases from 1.0.

The test conditions for the data shown in FIGS. 3 and 4 are as follows, and these test conditions indicate the conditions when 1-painting is performed at P2.

a, r? Type: Melamine alkyd (black) Viscosity: 22 seconds/20'C with Ford cup #4 [], Coating machine: Minibell (16,000 rpm)
Shaping air 0.2, Okg/cm2 C0 Kanodegawa: Sprayed in 2 parts, 1st time,
, 10Occ/min 2nd time, 150-200cc/min, Cerading time = 1o min x room temperature e, Baking conditions +140''c x 25 molecules, Base smoothness: 0.6 (PGD value ) (Intermediate coating, PE table) g1 Rotation or reversal operating range: Cerading (10 minutes) to baking (10 minutes) h, Painted on the side of a rectangular cylinder with a knee side of 30 cm, rotatable at the center Support], Rotation speed of the embossed object: 6 rpm, 3Or 1
Nom.

The rotation was carried out at three different speeds of 60 rpm, but there was no difference due to the difference in rotational speed.In addition, the water axes described here include those with an inclination range of about 10° from the water axle. shall be held.

(The following is a blank space) Figs. 16 to 20 are diagrams showing the dripping characteristics of a thermosetting paint when a thermosetting paint is used as the paint used in step P2. Note that the sending and ending process was performed at a temperature of 20° C. for 10 minutes. Further, in the baking step, the temperature was increased from 20° C. to 140° C. for 8 minutes, and the temperature was then maintained at 140° C. for 25 minutes.

In FIGS. 16 to 20, examples of a total of 11 types of thermosetting paints are shown, and the specific test conditions for obtaining such data are as follows. In addition,
In the following description, things that are not particularly differentiated from paint examples a to a are common matters.

(1) Paint/Solvent dilution thermosetting Melaminal Kid (hue black) - Dilution solvent triol 4% (wt%) Tsurupetz 10
0 3% (weight %) (manufactured by Esso) Truvet 200 3% (weight %) (manufactured by Esso) ・Anti-sagging agent Pre-crosslinked acrylic resin, all numbers indicating the amount added are Ichikawa % based on non-volatile content. It is shown in Table 1 along with the viscosity.

- All viscosity values are expressed in Ford Cup #4/20°C and are shown in Table 1 along with the content ratio of anti-sagging agent.

(2) Painting conditions Table 2 shows two-stage blowing.

Note that the cerading and baking are as described in 1iiii.

(3) Test plate/cold rolled steel plate with phosphoric acid! 1 [i Lead treatment / Undercoat cationic electrodeposition 170℃ x 25 minutes baking: film thickness 25μm ・Intermediate coating 140℃ x 25 minutes baking: film thickness 40μm ・Intermediate coating wet sanding Complete wet sanding with #800 waterproof abrasive paper (4) Evaluation method: With the test panel (3) above set vertically, a top coat was applied under the above-mentioned coating conditions while varying the viscosity of the paint and the content of the 1L anti-sag agent. Examples of paints that do not sag for at least 1 minute after completion of painting and cause sag after 1 minute are shown in FIGS. 16 to 20.

In particular, the paints e and f shown in Fig. 17 do not sag until the baking process after painting is completed, so even if the takt of the painting line is 1 minute, it can also be applied to a line with a post-correction process. 1 minute adaptable. Of course, it goes without saying that the present invention is not limited to such paints.

Table 1 (Viscosity, drip prevention agent content) Here, the rotational speed of the body W can be adjusted according to the maximum dripping speed of the paint to a speed that will not cause dripping even at the maximum dripping speed. To explain this point concretely, let us consider a case where the maximum sagging speed is, for example, 10 minutes and 12 mm, and the allowable range of the sagging speed is, for example, 1 mm per minute or less4. The time it takes for someone to appear is 5 seconds, so during this 5 seconds, the body, fW
If the direction of the small force acting on the surface is reversed by 180 degrees, sag will be prevented. Therefore, rotating the body W by 180 degrees in 5 seconds means that the rotation speed of the body W should be at least greater than 6 I·pm.

By the way, the paint tends to accumulate at the corners that form the boundary between the vertical surface extending in the width direction and the horizontal surface extending in the left-right direction. This paint buildup ends up being a local thickening of the paint film, which is where the maximum dripping speed occurs. Therefore, when the paint is sprayed to a predetermined film thickness, it is necessary to determine the rotational speed of the body W by taking into account the accumulation of paint. However, when the body W is rotated in a reversal manner in which forward rotation and reverse rotation are repeated 1"j, the above-mentioned accumulation hardly occurs. There is no need to consider it.

Of course, the rotational speed is not set as the minimum necessary value according to the maximum sagging speed, but is set to a certain extent, for example, at least 2 to 3 times higher than the rotational speed obtained from the above calculation example.
It is recommended to set the speed to a relatively high speed.

The upper limit of this rotational speed can be set as appropriate within a range that does not cause paint to sag due to centrifugal force. An example of a fixture used for rotatably supporting the body in the water direction will be described.

Figure 5 shows the front jig l attached to the front part of the body W.
This jig IF consists of a pair of left and right mounting brackets 2, a pair of left and right stays 3 welded to each of the left and right brackets 2, and a connecting bar that connects the left and right pair of stays 3. 4, and a rotating shaft 5 integrated with the connecting bar 4. Such a jig 1 has a bracket 2
The portion is fixed to a front strength member of the body W, such as the front end of the front sight frame 11. That is, since a bracket 12 for attaching a normal bumper (not shown) is welded to the front side frame 11, the bracket [・2] is attached to the bracket 12 on the body W side.
are fixed using bolts (not shown).

On the other hand, the rear jig IR attached to the rear part of the body W is shown in FIG. This rear jig lR is also the front jig f4. ．． It has a similar configuration to IF, and this ij
Components corresponding to the side jig IF are given the same reference numerals. To attach this rear jig IR to the body W,
This is done by using the bracket 2 as a strength member at the rear end of the body W and fixing it to the floor frame 1113 with bolts. Of course, a bumper mounting bracket is welded to the rear end of the floor frame 13 to which a bumper is generally attached, so this bumper mounting bracket can be used to attach the rear jig IR. Installation can also be done.

When the front and rear jigs 1F and IR are attached to the body rW, their rotating shafts 5 are connected to the ii of the body W.
i They are positioned on the same straight line extending in the rear direction.

This same straight line is the axis of rotation °C of the body W, and preferably, this axis of rotation passes through the center G of the body W (see Fig. 7). Note that the rotation axis C is 1
By passing through the center (j), large fluctuations in the rotational speed are prevented when the body W rotates.This prevents shocks from occurring in the body W due to rotational fluctuations. 1, which is more preferable in terms of anti-drip IL.

Note that the jigs IF and IR before and after 1 are dedicated in advance according to the vehicle type (type of Bob 2 and W).

Saren at least P3. This is a trolley used in P4 and has the function of rotating the body W.

In FIG. 7, the trolley has a base 21, and this base 2
Wheels 22 attached to the vehicle 1 are run on a road surface 23. This base 21 has one front support 24, two intermediate supports 25, 26, and one rear support that extend upward in sequence from the front side in the running direction to the rear side (from the right side to the left side in FIG. 7). The support space 28 has a support column 27, and the lid between the intermediate column 25, 26 and the rear column 27 is thick in the front-rear direction (with a spacing of 17X).

The body W is disposed in the support space 28, and its front part is rotatably supported by two pairs of Φ support columns 26 using the front jig IF. 11 and is rotatably supported by the rear support 27.

The front and rear jigs 1 [′, 1 ((rotation shaft 5) are capable of being freely engaged with and detached from the support columns 26 and 27 from the double direction, and the rear jig IR is rotated in the direction of the rotation axis β. For this reason, the intermediate strut 26 is formed with a notch 26a that opens on its upper end surface (see FIGS. 10 to 12), while the rear strut 27 has a notch 26a that opens on its upper end surface. Notch 2 to open
7a is formed (see FIG. 1O, FIG. 14, and FIG. 15). These notches 26a and 27a are formed by the jig IF,
The size is such that the rotating shaft 5 of the IR can fit therein. A flange portion 5a is formed on the rotating shaft 5 of the rear jig IR, and a notch 27b having a shape corresponding to the flange portion 5a communicating with the notch 27a is formed in the rear support 27. . As a result, the rear jig IR is engaged with and disengaged from the notches 27a and 27b of the rear column 27 from above and below, and is made immovable in the front and rear direction with respect to the rear column 27 by the stopper action of the flange portion 5a. Ru. Note that the rotational force is applied to the body W via the rotation shaft 5 of the front jig IF, and for this reason, the tip of the rotation shaft 5 of the ni1 jig IF is provided with a connecting portion 5b (see FIG. 5), which will be described later. (see also) is formed.

A stay 29 is provided to protrude downward from the base 21,
A traction wire 30 is connected to the lower end of this stay 29. This wire 30 is of an endless type,
It is driven in one direction by a dryer (not shown), and thereby the trolley is driven in a predetermined transport direction. Of course, the motor is installed in a safe location from an explosion-proof point of view.

The rotation of the body W uses the movement of the trolley.

That is, this is performed by utilizing the displacement of the bogie relative to the running road surface 23. A rotation extraction mechanism 31 for extracting the displacement of the truck as rotation is configured as follows.

That is, the rotary take-out mechanism 31 is configured by a rotating shaft 32 that is extended and rotatably supported in the vertical direction on the base 21, a sprocket 33 fixed to the lower end of the rotating shaft 32, and a sprocket 33 that meshes with the sprocket 33. The chain 34 is made up of a chain 34. This chain 34 is disposed in parallel with the wire 30 in an immovable state with respect to the running road surface 23.

This ensures that when the trolley is towed via the wire 30, the chain 34 is immovable;
The rotating shaft 32 is rotated accordingly.

1) The rotation of the rotation shaft 32 is controlled by the front jig I'([[:
The transmission mechanism 35 for transmitting the signal to the rotating shaft 5) is constructed as follows. That is, the transmission mechanism 35 is
a casing 36 fixed to the rear surface of the front strut 24;
A rotary shaft 37 is extended and rotatably supported in the front-rear direction in which the lateral force is directed to the casing 36;
A pair of bevel gears 38 interlocking with the rotating shaft 32
．． 39, and a connecting shaft 40 held at E, which is rotatable with respect to the intermediate support 25 and slidable in the front and rear directions. (The engaging portion is indicated by the reference numeral 41 in FIG. 7).

When the rotating shaft 32 is thereby rotated, the connecting shaft 40 is also rotated. Of course, the rotating shaft; 37 and the connecting shaft 40
3° 1111 connecting shaft 40 installed so as to rotate 1lIIIl line ℃ ℃ 1 device is +ji7 side adjustment! -, L I
In other words, as shown in FIGS. 1O to 12, the left end of the rotating shaft 5 for the RIIF jig 1F has a cross-shaped connecting portion 5b. is formed at the end of the connecting shaft 40.
As shown in Fig. 33, a box portion 40a is formed into which the connecting portion 5b is fitted without play. By sliding the connecting shaft 40 through the rod 43, the box portion 40a (engaging recess 40c) and the connecting portion 5b are engaged and disengaged, and when engaged, the connecting shaft 40 and the rotating shaft 5 are connected to each other by force. It is said that it is possible to rotate integrally.
As shown in FIG.
It is fitted into an annular groove 40b formed on the outer periphery of a.

With the above configuration, by lowering the body W onto the trolley while the connecting shaft 40 is displaced to the right in FIG. is rotatable and 1r by the intermediate support 26.27.
7 supported in an immovable state in the rearward direction, and then the connecting shaft 4
0 (locking recess 40c>).

1i;1 Yakai! Rotation shaft 5 (connection part 5b) at
is engaged with. As a result, when the trolley is pulled via the wire 3o, the body W is rotated about a predetermined horizontal axis C. In addition, the stand of body W [1j
I) To remove from 1r
That's fine.

(Effects of the Invention) As is clear from what has been described below, the present invention utilizes the fluidity and rotation of paint to produce high-quality products with higher smoothness than conventional paints with the same paint thickness. A painted surface can be obtained.

In addition, since the rotation speed of the object to be coated is set according to the maximum drip speed, it is possible to reliably prevent "n" conditions such as paint dripping due to insufficient rotation speed. .

[Brief explanation of the drawing]

FIG. 1 is an overall process diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing how the posture of the automatic Ichikawa body, which is the object to be coated, changes as it rotates. Figures 3 and 4 show the thickness and sag of the paint and the flat surface of the painted surface.)
A graph showing the relationship between degrees and rotation. FIGS. 5 and 6 are perspective views showing examples of jigs used to rotate the body. FIG. 7 is a side view showing an example of a body transport trolley in which the body can be rotated. FIG. 8 is a partially cutaway plan view showing the state below the running path of the bogie. FIG. 9 is a sectional view taken along the line X9-X9 in FIG. FIG. 10 is a side cross-sectional view showing the joint portion between the rotating jig and the truck. FIG. 11 is a sectional view taken along the line X1l-Xll in FIG. 1O. FIG. 12 is a side view of FIG. 11. FIG. 13 is a sectional view taken along the line Xl3-Xl3 in FIG. 10. FIG. 14 is a sectional view taken along the line Xl4-X] in FIG. 10. FIG. 15 is a side view of FIG. 14. Figures 16 to 20 are diagrams showing the maximum dripping speed and dripping characteristics of paint. P I-P4: Process W: Body flow: Rotation axis ■): Transfer table 1li 1F, IR: Rotation jig

Claims (1)

[Claims] (1) In a painting method comprising a painting process of applying paint to an object to be painted, and a drying process of drying the paint applied to the object, in the drying process, large amounts of paint that may cause sagging of the paint are provided. The object to be coated is rotated around a substantially horizontal axis until the paint is cured until it becomes fluid and no longer drips, and the rotational speed of the object in the drying process is set to the maximum dripping speed of the paint. A painting method characterized by: